The present invention relates to a sheet finishing apparatus in which sheets, on which images are formed by an image forming apparatus such as an electrophotographic copier, a printer, a printing machine, or the like, are received, and finishing processings such as stapling by a stapler, shifting processing, and similar processing, are conducted, and then, the sheets are ejected onto an exit tray by a sheet ejecting means.
A sheet finishing apparatus, which is called a finisher, is used as an apparatus in which a plurality of sheets, on which images have been recorded and which are delivered from the image forming apparatus, are aligned for each copy volume and stapled by a stapler.
This finisher is connected to an image forming apparatus main body such as a copier, a printer, or a similar apparatus, in its function, and is driven corresponding to sequence operations of a copying, or printing process.
Accordingly, for an image forming apparatus by which a large number of sheets with images are processed at a high speed, a finisher is necessary which can follow the processing speed of the apparatus for achieving its functions, and by which a large number of sheets can be processed at a high a-rs speed.
Proposals for this type finisher in which high speed processing can be conducted, are disclosed in Japanese Patent Publication Open to Public Inspection Nos. 142359/1985, 158463/1985, 239169/1987, 288002/1987, 267667/1988, 276691/1990, and Japanese Patent Publication No. 41991/1993.
Sheets, on which images have been recorded, conveyed from the image forming apparatus main body, are sequentially stacked, being aligned, in an intermediate stacker. After sheets have been stacked for each one set of sheets, sheet finishing such as stapling, or the like, is conducted. The stapled set of sheets is put on a delivery belt provided in the bottom portion of the intermediate stacker and conveyed, held by a pair of upper and lower sheet delivery rollers, and delivered onto an exit tray.
A sheet finishing apparatus, described in Japanese Patent Application No. 42728/1996, (which matured into Japanese Patent Publication Open to Public Inspection No. 235069/1977), is provided with a stapler and an exit tray corresponding the stapler. A sheet finishing apparatus, described in Japanese Patent Publication Open to Public Inspection No. 76190/1995, is provided with 2 staplers and 2 exit trays corresponding to the staplers.
In a conventional sheet finishing apparatus, sheets, on which images are formed, conveyed from the image forming apparatus, are finishing processed by a sheet finishing processing means (staplers, shift means, bookbinding means, punching means, etc.), and after that, delivered onto an exit tray by a sheet ejecting means, slide down along an exit tray surface arranged being inclined, and trailing edge portions of the sheets come into contact with a stopper and stop. In this connection, a sheet, for which finishing is not necessary, is directly delivered onto fixed exit tray, slides down along the exit tray surface arranged being inclined, and the trailing edge portion of the sheet comes into contact with the stopper surface and stops.
Problems in the conventional sheet finishing apparatus will be listed below.
(1) As the number of sheets delivered and stacked on the exit tray means, on which sheets finishing processed by the sheet finishing apparatus are stacked, are increased, the height of the stacked sheets is increased. Accordingly, a sheet height detecting means is provided so that sheets do not interfere with a delivery path, and the exit tray means is controlled to be lowered so that the height of sheet stacking surface is constant. Accordingly, a control system and mechanism become complicated.
(2) When finishing processed sheets are delivered by the sheet ejecting means, and stacked on the sheet stacking surface of the exit tray means having an inclined surface in which the leading edge portion is higher, the leading edge portion of the large sized sheet projects and hangs down from the leading edge portion of the exit tray means, and further, is sliding-contacted with a succeeding delivery sheet and pushed out, resulting in possibility of sheet falling down from the sheet stacking surface of the exit tray means. When the sheet stacking surface is enlarged for preventing the sheet falling down, the size of the sheet finishing apparatus is increased, resulting in a problem in which the mounting space is increased.
(3) Also when no-finishing processed sheet is stacked on the stacking surface of the exit tray means (non-sort tray) of the sheet finishing apparatus, there is a problem of sheet falling down caused by hanging down of the leading edge portion of the sheet, and a problem in which the leading edge portion of the hanged down sheet contacts an elevating exit tray provided below it.
A sheet finishing apparatus disclosed in Japanese Patent Publication Open to Public Inspection No. 276691/1990, is structured in such a manner that 2 fur-brushes are rotatably provided and the leading edge portion of the fur-brush is in contact with a guide plate. A sheet finishing apparatus disclosed in the sheet accommodating apparatus in Japanese Patent Publication Open to Public Inspection No. 214565/1989, is structured in such a manner that a paddle wheel, on which a plurality of blade members are radially provided, is rotated for aligning the sheet. A sheet finishing apparatus disclosed in Japanese Patent Publication Open to Public Inspection No. 116168/1988, is structured in such a manner that a portion of a belt, whose lower end portion is in contact with an intermediate tray, is wound around a lower roller of a delivery roller pair, the belt is rotated with the lower roller, and causes the sheet conveyed on the intermediate tray to contact with a stopper.
A sheet finishing apparatus disclosed in Japanese Patent Publication Open to Public Inspection No. 127556/1989, has a first and a second sheet conveyance paths which convey sheets sent from the image forming means to the sheet finishing means, a conveyance direction switching means for switching the first and the second sheet conveyance paths, and a control means for controlling the conveyance direction switching means so that the sheet is sent to the second conveyance path corresponding to the operation of the sheet finishing apparatus.
The conventional sheet finishing apparatus has one exit tray which can go up and down, for one sheet finishing processing means (a stapler, a shift means, a bookbinding means, punching means, etc.). The exit tray has a fixed bottom surface on which sheets are stacked, and the overall exit tray is driven upward and downward by a driving source corresponding to the number of sheets stacked on the fixed bottom surface of the exit tray. Accordingly, the maximum number of sheets accommodated on one exit tray is limited.
Further, when sheets outputted in different image forming modes, (for example, sheets outputted in a copy mode, and sheets outputted in a printer mode), are successively delivered onto the exit tray after respectively finishing processed, sheets in both modes are mixed on the exit tray, and a problem occurs in which sheet sorting is difficult.
Furthermore, when sheets processed in different finishing processing modes, (for example, stapling processed sheets, and shifting processed sheets ), are successively delivered on the exit tray, sheets in both modes are mixed on the exit tray, resulting in a problem of difficult sheet sorting.